A number of methods for debonding/separating two substrates (product substrate and carrier substrate) are known from the state of the art. Most methods use so-called bonding adhesives for achieving a temporary bond between two substrates, which can be easily undone. The bonding adhesives are normally polymers, in particular thermoplastics.
A first method for the temporary bonding includes coating the entire surface of a substrate. The second substrate is connected to the first substrate by a bonding operation. Separation, i.e. debonding of the two substrates is effected by a shearing process at a raised temperature. This temperature preferably lies above the glass transition temperature of the bonding adhesive. Due to the shearing force applied it is possible to move both substrates relative to each other in a very slow process and thus to separate them from each other.
A second method for temporary bonding includes treating specific surface areas of the carrier substrate in such a way that the adhesive effect between these surface areas and the bonding adhesive is minimal, in particular completely disappears. Apart from these specifically treated surface areas a very small surface area remains, which is left untreated. This highly adhesive surface area is normally a peripheral circular ring a few millimetres thick. Following this specific treatment the carrier substrate is coated full-surface with the bonding adhesive. Then follows a normal bonding operation. The debonding operation is usually carried out by chemical means in that the rim zone of the bonding adhesive is debonded, thereby reducing the adhesive power between the bonding adhesive and the carrier substrate. Thereafter the carrier substrate can be very easily lifted off the product substrate.
A further method for separating two substrates from each other includes applying a special soluble layer onto, in particular, a transparent carrier substrate, before the bonding adhesive is applied. Because the carrier substrate is transparent to a specific electromagnetic radiation, the photons are allowed unhindered access to the soluble layer. The photons cause a change in the soluble layer, reducing the adhesive power to the bonding adhesive. Such a method has been described in WO2014058601A1, in which a UV laser is fired onto a soluble layer on the inside of a carrier substrate in order to obtain a reaction there, which causes the bonding adhesive to separate from the carrier substrate and thus causes the carrier substrate to separate from the product substrate.